Cars are a major source of fuel consumption world wide. The principal fuels in use today are petroleum derivatives such as gasoline and diesel. These are fossil fuels that tend to pollute, and there have long been discussions about changing to cleaner and more renewable sources of energy. These are called "alternative fuels" and along with traditional environmental concerns, the constantly increasing gas prices have made alternative fuels a hot topic for discussion once again...Biodiesels, alcohols, and electric cars are all alternatives to the current way of doing business. So how do they work?
NOTE: For more on alternative fuels see: "Soaring Gas Prices...Is There an Alternative?"
Well, first let's look at gasoline and diesel: They are commonly used in what is called the internal combustion engine. The liquid fuel (i.e., gas that you fill the tank with) is drawn into a chamber containing a piston. The fuel undergoes combustion when mixed with oxygen and ignited. This results in hot gases that expand, driving the piston down and producing motion used to drive the car. This is a prime example of chemical energy being transformed into mechanical energy.
Did you know? The traditional internal combustion engine converts chemical energy into mechanical energy to power the movement of a car.
Several of the alternative fuels, such as biodiesels and alcohol, work on this principle. These two alternative fuels are volatile liquids, meaning that they vaporize quickly which allows them to mix easily with oxygen gas and undergo combustion.
Did you know? Biodiesel and alcohol power a vehicle using the same principle as the internal combustion engine (i.e., chemical energy is converted to mechanical energy).
Biodiesel can be derived from vegetable oil, animal fat and recycled grease, but it has long been ignored since it was more expensive than petroleum fuels. However, it is cleaner and is renewable.
Alcohols, such as ethanol, are another renewable source of energy that can be derived from vegetables. Brazil is the leader in using ethanol from sugarcanes as an alternative fuel. But the use of biodiesels and alcohols, require modifications to the internal combustion engine, which was designed to work with petroleum based products. So to get around this obstacle, mixtures of petroleum fuels with biodiesel or alcohols have been used in several countries.
The other approach is the electric car, which has been around since the 1830's. An electric motor converts electrical energy into mechanical energy resulting in motion. Electrons passing through a wire produce an electric current which has its own magnetic field. Such magnetic fields push and pull on each other causing motion. The source of the electric energy can be from a battery, which has stored chemical energy, from the sun via solar panels, or from fuel cells.
Did you know? Electric vehicles work by converting electric energy into mechanical energy.
Fuel cells and batteries work in a similar fashion. They consist of an anode, where oxidation or a loss of electrons occurs, and a cathode, where reduction or a gain of electrons occurs. These are connected by a permeable membrane or ion channel (in the case of the battery) through which positively and negatively charged ions can pass, as well as a conducting wire through which electrons can pass. These electrons provide the electric energy used to drive the motors. This, however, is where the similarities stop. While batteries, even the rechargeable ones, have a pre-set amount of reactants, fuel cells were designed to be replenished. This is what makes fuel cell technology attractive over battery driven electric cars.
Did you know? All batteries have a "lifespan" since they have a pre-set amount of reactants that are used to create electric energy; fuel cells are designed to be replenished.
The reactants of a fuel cell are oxygen and hydrogen and the byproduct is water, making fuel cells environmentally friendly. The hydrogen is split into a proton (H+) and an electron at the anode. The proton travels through a membrane to the cathode where the oxygen is present; the electron, however, travels through an external circuit before ending up at the cathode as well. Then they all react (O2, the protons, and the electrons) forming water, an environmentally friendly waste-product.
Did you know? The reaction in a fuel cell is: O2 + 4H+ + 4e » 2H2O
The biggest problems with fuel cells are: 1) that hydrogen is not readily available, and 2) fuel cells are not yet road hardy. However electric cars are appearing on the road in the forms of hybrids. These cars have a petroleum based engine but are also electrically driven at the same time. The gasoline or diesel engine is used to drive the machine but, at the same time, to also generate electricity which can be stored in a battery or used instantly to aid in the driving of the car.
There are many different options for alternative fuels, and not all have been outlined in this essay. Whether they will replace the current fuels or not will be determined by a mixture of need, social consciousness, practicality, and most importantly price.
Article First published July 24, 2006
Demirbas A. 2005. Progress in Energy and Combustion Science, 31: 466-487
Kiss AA, Dimian AC, Rothenberg G. 2006. Adv. Synth. Catal. 348: 75 — 81
Manzini F. 2006. International Journal of Hydrogen Energy, 31:327-335.
Urquhart I. "Should Ontario control prices at gas pump?". The Toronto Star, July 12, 2006.
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Vlad Martin-Diaconescu has a BSc from the University of British Columbia in Honours Biochemistry and is currently a PhD student in the UBC Chemistry Department. His research investigates reactive biological intermediates and new methods of detecting and analyzing them. What Vlad likes most about Science is that he always gets to try new things that he is not very familiar with. Even better, he gets to try to figure out how these things work and how to apply them to his research. Vlad also enjoys telling other people about Science, which is what attracted him to write about it.